STRETCH-SHORTENING CYCLE AND RELATIVE

STIFFNESS AND ITS EFFECT ON RUNNING ECONOMY IN

FEMAL COLLEGIATE DISTANCE RUNNERS FOR THE

ONE MILE RUNJ.Whitaker, C.Binns, L.Capello, S.Titus, M.Johnson, M.Petruzzelli

PE 200 Applied Kinesiology

Keene State College

Keene, New Hampshire

Introduction

Good running economy is important to performance in distance running.

A factor of running economy is the stretch-shortening cycle (SSC). The SSC is an active stretch (eccentric contraction) of a muscle followed directly by shortening ( concentric contraction ) of the same muscle.

The ability of muscles to store and return elastic energy effectively is important in movements that involve the SSC such as running.

The SSC provides a physiological advantage

The muscle generates more force and is more efficient during the concentric contraction when compared with the same contraction without the preceding eccentric contraction.

The muscle does more work per unit of metabolic energy input

Storage and return of elastic energy

Introduction

Relative stiffness in the lower body is shown to help with good running economy.

Stiffer runners were the most economical.

Introduction

The purpose of this study is to show that relative stiffness and the stretch shortening cycle will create a good running economy for female distance runners in the one mile.

Methods

• Six college-age female subjects ages 19-21 volunteered to participate in this study; all six of these females are distance runners on the Keene State Track and Cross Country teams. All subjects have been running 40 to 55 miles a week and have trained 6 to 7 days a week for a least 9 months prior to the study. None have taken part in a regular weight training program for at least 9 months. The exercises being tested will relate directly to the power, and stiffness of the runners legs.

• The exercises included are the sit and reach and the vertical jump test. The vertical jump test will measure the counter movement jump, and static jump both preformed on the dominant foot, and then the non dominant foot.

Methods

All subjects were warmed-up prior to testing. Running three to five miles.

After running subjects preformed the sit and reach test once for both legs to test flexibility in the legs.

When the runners completed the sit and reach test they were tested on their vertical jumps for power output.

Sit and Reach

The sit and reach test will be administered to the runners using the sit and reach box. The leg being tested will be flat against the ground and the foot will be flat against the back of the box. The opposite leg will be to the side and out of the way. The runners hands will be flat one on top of the other. The runners will reach their furthest pushing the metal measuring tool, relax, push their furthest, relax, and then push their furthest and hold it for 1 second.

Vertical Jump

The runners were allowed one practice jump for the static and counterbalance jump on each leg. The runner will complete both jumps from each leg two times. The jumping legs will be alternated each time.

To measure vertical jump we used a switch mat “Just Jump”. This measure time spent in the air and converts it into vertical jump.

Runners performed every jump with their arms folded across their chests.

Each runner was given an accurate visual demonstrations of what the counter jump and static jumps looked like.

Methods

One mile run times were taken from subjects personal records in track competitions during the 2009-2010 indoor track competitions.

Results

Sub 1 Mile (min:sec) CMJ R (in) CMJ L (in) SJ R (in) SJ L (in) S&R R (in) S&R L (in)1 5:26 5.7 6.8 5.8 5.9 45 46.22 5:14 7.9 7.8 6.7 6.2 42.1 403 5:11 10.8 9.9 8.2 8.3 34.5 364 5:20 9.2 7.4 5.9 6.8 40.5 40.15 5:53 4.9 4.8 3.7 4.2 32 316 4:49 10.2 9 8.4 8.7 34 34

Pearson Value to 1 Mile -0.825514565 -0.871761402 -0.943136463 -0.927124279 -0.045676 -0.0934084

Conclusion

Statistical evidence shows that there is a high correlation between the runners vertical jump, and their mile time.

The evidence also shows that there is almost no correlation between the sit and reach and the mile time.

A possible reason for the low correlation between the mile time and the sit and reach is height and arm, leg length were not taken into account. Sit and reach is not the most accurate test for flexibility.

Practical Application

This information can be used by runners, running coaches, and strength and conditioning coaches.

Practical Application

With this information athletes and their coaches can gain a better understanding for the stretch shortening cycle and how important it is for distance runners to have leg power. Having this knowledge coaches will have the ability to help their athletes and runners will be able to help themselves by doing strengthening exercises for their legs such as squats and lunges.

The results of this study suggest that implementing a lower body strength training program in previously untrained female distance runners may have positive results on running economy. The improvement in running economy could take vital seconds off of a runners time and it is these seconds that determine race placement as well as qualifying marks.

References

1. Arampatzis, A, Bruggemann, G, & Metzler, V. (1999). The Effect of speed on leg stiffness and joint kinetics in human running. Journal of Biomechanics, 32(5), 1349-1353.

2. Harrison, A. J, Keane, S. P., & Coglan, J. (2004). Force-velocity relationship and stretch-shortening cycle function in sprint and endurance athletes. Journal of Strength and Conditioning Research, 18(3), 473-479.

3. Johnson, R. E., Quinn, T. J., Kertzer, R, & Vroman, N.B. (1997). Strength training in female distance runners: impact on running economy. Journal of Strength and Conditioning Research, 11(4), 224-229.

4. Saunders, P.U., Telford, R.D., Pyne, D.B., Peltola, E.M., Cunningham, R.B., Gore, C.J. & Hawley, J.A. (2006) Short-Term Polymeric Training Improves Running Economy In Highly Trained Middle and Long Distance Runners. The Journal of Strength and Conditioning Research, 20(4), 947-954.

5. Slawinski, J, Heubert, R, Quievre, R, Billat, V, & Hannon, C. (2008). Changes in spring-mass model parameters and energy cost during track running to exhaustion. Journal of Strength and Conditioning Research, 22(3), 930-936.

6. Trehearn, T.L., & Buresh, R.J. (2009). Sit-and-reach flexibility and running economy of men and women collegiate distance runners. Journal of Strength and Conditioning Research, 21(1), 158-162.

7. Turner, A.M., Owings, J, & Schwane, J.A. (2003). Improvement in running economy after 6 weeks of plyometric training. Journal of Strength and Conditioning Research, 17(1), 60-67.

8. Yamamoto, L.M., Lopez, R.M., Klau, J.F., Casa, D.J., Kraemer, W.J., & Maresh, C.M. (2008). The Effects Of Resistance Training On Endurance Distance Running Performance Among Highly Trained Runners: A Systematic Review. The Journal of Strength and Conditioning Research, 22(6, 2036-044.